Polyurethane

Plastic pipe with insulation. The red pipe, and the black mantle are made of polyethylene, the yellow-brown foam is made of polyurethane

Polyurethane is a polymer. Its name is often shortened to PU or PUR. Polyurethane is made of organic units, which are joined by urethane. Polyurethane polymers are formed through step-growth polymerization. In this process, a monomer containing at least two isocyanate functional groups reacts with another monomer containing at least two hydroxyl (alcohol) groups in the presence of a catalyst.

Polyurethane is available with different levels of stiffness, hardness or densities. Examples for such materials are:

• Low-density flexible foam used in upholstery
• Low-density rigid foam used for thermal insulation and RTM cores
• Soft solid elastomers used for gel pads and print rollers
• Low density elastomers used in footwear
• Hard solid plastics used as electronic instrument bezels and structural parts

Polyurethanes are widely used in high resiliency flexible foam seating, rigid foam insulation panels, microcellular foam seals and gaskets, durable elastomeric wheels and tires, automotive suspension bushings, electrical potting compounds, high performance adhesives and sealants, Spandex fibers, seals, gaskets, carpet underlay, and hard plastic parts.

Polyurethane products are often called "urethanes". They should not be confused with the specific substance urethane, also known as ethyl carbamate. Polyurethanes are not produced from ethyl carbamate, nor do they contain it.